1. Field of the Invention
The present invention relates to an automatic power control filter circuit for controlling laser power irradiated to an optical disc and an optical disc device provided with the automatic power control filter circuit.
2. Background Art
A conventional optical disc device discriminates various kinds of optical disc media, and performs control for reproducing and recording operations corresponding to the respective media.
For example, read-only CD-ROM and DVD-ROM, write-once CR-R and DVD-R, rewritable CD-RW and DVD-RW, or the like, are different from each other in the recording power and the reading power of a laser diode, and hence, it is necessary for the optical disc device to control the drive current of the laser diode.
Among these conventional optical disc devices, for example, there is an optical disc device provided with a laser which performs the recording or reproducing operation by irradiating an optical disc with light, a light monitor element which receives a part of the light emitted by the laser in the direction of the optical disc, a correcting device which outputs a correction signal obtained by non-linearly correcting an output signal of the light monitor element in accordance with a level of an input signal of a laser power driving device or a level of an output signal of the light monitor element (light emission monitor signal), and the laser power driving device which drives the laser in accordance with the input signal and the correction signal (see, for example, Japanese Patent Laid-Open Publication No. 2003-308623).
Here, a procedure is often performed for determining the optimum recording power by making a recording operation performed with the power optionally changed with respect to a recording power initial value, and by making the quality of a reproduced waveform after the recording operation measured. The procedure is referred to as optimum power control (OPC) in the optical disc industry.
However, in the case where the correcting device is, for example, constituted in such a manner that when a recording power fine adjustment coefficient is changed, errors between input data corresponding to light emission monitor signals and data corresponding to a target power are integrated, there is a problem that it takes much time until the output of the laser is stabilized, in the case of an optical disc device having a narrow loop band.